Unsaturated fatty acids include one or more double bonds (equally known as unsaturations). Oleic acid found in olive oil has 1 double bond.

The double bond of an unsaturated fatty acid creates a “bend” in the molecule.

Triglyceride

Hence, the more double bonds the fatty acid contains, the more complex its structure will be. Because of their cumbersome structure, the fatty acids present in the oil compact together with difficulty. And, as a result, oils containing large amounts of unsaturated fatty acids are liquid at ambient temperature.

Furthermore, the more double bonds the fatty acid incorporates, the higher the rate of oxidation, and the faster the oil turns rancid.

Depending on their fatty acid composition, oils will be able to progressively penetrate the hair fibre or else to remain on the surface of the cuticle.

Penetrating oils and natural afro hair.

Properties of penetrating oils.

The ability of an oil to penetrate the hair depends on its fatty acid composition. As a matter of fact, the shorter fatty acids are included in the oil, the more the oil is able to infiltrate the hair fiber. Additionally, certain fatty acids display a slight positive charge and will be attracted by the negative charges of the hair proteins. These so-called “polar” fatty acids present a high affinity for hair proteins [1].

Which are the penetrating oils?

Coconut oil [INCI: Cocos Nucifera (Coconut) Oil] contains lauric acid. This small fatty acid has a strong affinity for hair proteins. When applied to the hair, this oil is able to penetrate deeply into the cortex and to diminish protein loss [2].

Coconut oil is a penetrating oil

Murumuru Butter [INCI: Astrocaryum Murumuru Seed Butter] and Babassu Oil [INCI: Orbignya Oleifera (Babassu) Seed Oil)] also include a high amount of lauric acid and would as well be able to penetrate the hair.

The oils listed above are the only oils studied by the scientific community for their penetration property. This does not mean that other oils are not able to penetrate the hair. They have not been the subject of studies yet.

What types of hair will benefit from the advantages of penetrating oils?

In fact, damaged hair has a porous cuticle. When immersed in water, it will absorb a large amount of water and will excessively swell. Their cuticle will rise and can break more readily, which will make the hair even more porous.

Furthermore, too much water in the hair will undermine the proteins of the cortex and will make the hair extremely elastic.

The disproportionate absorption of water, followed by a repeated shrinking of the hair fibre (hygral fatigue) will also weaken the hair.

The use of a penetrating oil will regulate the entry of water into the hair fibre. The oil will seize the free space in the hair and, as a result, will slow down the water influx. Besides, it will make the hair more likely to repel water and a healthy hair is a hydrophobic hair (which does not like water).

Sunflower oil is a penetrating oil

How to use penetrating oils?

Penetrating oils are particularly effective on damaged and porous hair as a pre-shampoo oil treatment. Allow working all night for maximum absorption. The heat also facilitates the penetration of oils into the hair.

Taking into account that these oils will penetrate the hair fibre, their presence on the surface of the hair will slowly diminish in favour of the cortex. Penetrating oils are therefore less effective in retaining moisture in the hair and reducing frizz (as in the LOC method, for example).

Coating oils and afro textured hair

Properties of coating oils.

Due to their composition rich in long and unsaturated fatty acids, these oils cannot infiltrate the hair fibre.

Non-penetrating oils have the ability to create a film around the hair, which will:

limit the evaporation of water and thus keep the hair hydrated longer,

diminish water absorption, reduce frizz and preserve the styling for a longer time.

Which are coating oils?

These are all other oils other than coconut, babassu, sunflower, olive and avocado oil.

Jojoba oil

Contrarily to its name, Jojoba Oil [INCI: Simmondsia Chinensis (Jojoba) Seed Oil] is not an oil but a liquid wax.

While vegetable oils are predominantly made up of triglycerides, jojoba oil is rich in waxy esters. Its composition is close to that of the human sebum [5].

Jojoba oil is sealing oil

Use of non-penetrating oils

Coating oils are suitable for all types of hair. They are extremely efficient for damaged hair as a sealing oil after application of leave-in.